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Abstract:

Usefulness of resource usage sensing information is determined by at
least one node in a radio system. Transmission of sensing result
information in the radio system is then controlled based at least in part
on the determined usefulness.

Claims:

1. A method comprising: determining usefulness of resource usage sensing
information in a radio system; and controlling transmission of sensing
result information in the radio system based at least in part on the
determined usefulness.

2. A method according to claim 1, where the determining comprises
determining by a first node the usefulness of the resource usage sensing
information for at least one second node.

3. A method according to claim 2, comprising performing at least one
spectrum sensing by the first node, and determining usefulness of the
result of the at least one spectrum sensing for at least one second node.

4. (canceled)

5. A method according to claim 1, comprising: estimating a usefulness
value of a spectrum sensing message for at least one node; choosing at
least one transmission parameter based on the estimated usefulness value;
and controlling transmission of the spectrum sensing message using the
chosen at least one transmission parameter.

6. A method according to claim 1, comprising controlling at least one of
transmit power, modulation scheme, coding scheme, quantization scheme,
amount of spectrum sensing data, number of retransmissions, time interval
between transmissions of spectrum sensing messages, use of antennae, and
the number of channels reported by the sensing messaging based on the
determined usefulness.

7. A method according to claim 1, comprising determining a parameter
based on the usefulness, and controlling sensing result messaging based
on the parameter.

8. A method according to claim 1, where the determining of the usefulness
comprises at least one of: estimating number of nodes in the radio
system; predicting usability of sensing information in a future point of
time; predicting frequency of future sensing information messages;
estimating level of noise in at least one radio channel; estimating the
probability for the presence of at least one primary user; considering
sensing results from at least one other node; and considering the number
of sensing results required to determine the absence of a primary user.

9. (canceled)

10. A method according to claim 1, where the controlling comprises
abstaining from sending a spectrum sensing message.

11. A method according to claim 1, where the usefulness is determined by
a secondary user, and the resource usage sensing comprises detection of
usage of resources by primary users.

12. A method according to claim 1, where the determining comprises
determining by a second node the usefulness of resource usage sensing
information provided in the radio system and the controlling comprises
sending from the second node a message to a first node.

13. A method according to claim 1, comprising communication of feedback
indicative of usefulness of sensing result information for at least one
second node.

14. (canceled)

15. A method according to claim 13, where the feedback comprises
information about at least one of: usefulness value for sensing
information for the reporting at least one second node; reception quality
of a spectrum sensing message; number of nodes in the radio system;
frequency of spectrum sensing messages; noise in at least one radio
channel; the probability for the presence of at least one primary user;
sensing results from at least one second node; request for more, less or
no sensing information; and number of sensing results required to
determine the absence of a primary user.

16-17. (canceled)

18. An apparatus for a radio system, the apparatus comprising: at least
one processor, and at least one memory including computer program code,
wherein the at least one memory and the computer program code are
configured, with the at least one processor, to cause determining of
usefulness of a resource usage sensing result in the radio system and for
controlling transmission of sensing result information at least in part
on the determined usefulness.

19. An apparatus according to claim 18, comprising a first control
apparatus for a first node in the radio system, the first control
apparatus being configured to provide sensing result information by means
of sensing radio resource usage in the radio system and determining the
usefulness of the sensing result for at least one second node.

20. An apparatus according to claim 19, where the first control apparatus
is configured to determine usefulness of the result of at least one
spectrum sensing.

21. An apparatus for a radio system, the apparatus comprising: at least
one processor, and at least one memory including computer program code,
wherein the at least one memory and the computer program code are
configured, with the at least one processor, to cause determining of
usefulness of sensing result information provided in the radio system and
sending of a message based on the determined usefulness of the sensing
result information.

22. An apparatus according to claim 21, comprising a second control
apparatus for a second node in the radio system, the second control
apparatus being configured to determine usefulness of sensing result
information provided by a first node and to send the message to the first
node.

23. (canceled)

24. An apparatus according to claim 21, wherein the apparatus is
configured to estimate a usefulness value of a spectrum sensing message,
choose at least one transmission parameter based on the estimated
usefulness value, and control transmission of the spectrum sensing
message based on the chosen at least one transmission parameter.

25. An apparatus according to claim 21, wherein the apparatus is
configured to control at least one of transmit power, modulation scheme,
coding scheme, quantization scheme, amount of spectrum sensing data,
number of retransmissions, time interval between transmissions of
spectrum sensing messages, use of antennae, and the number of channels
reported in sensing result information messages.

26. An apparatus according to claim 21, wherein the apparatus is
configured to at least one of: estimate number of nodes in the radio
system; predict usability of sensing information in a future point of
time; predict frequency of future sensing information messages; estimate
level of noise in at least one radio channel; estimate the probability
for the presence of at least one primary user; consider sensing results
from at least one other node; and consider the number of sensing results
required to determine the absence of a primary user.

27. An apparatus according to claim 21, wherein the apparatus is
configured to communicate feedback indicative of usefulness of sensing
result information between at least two nodes.

28. (canceled)

29. An apparatus according to claim 27, where the feedback comprises
information about at least one of: usefulness value for sensing
information for the reporting at least one second node; reception quality
of a spectrum sensing message; number of nodes in the radio system;
frequency of spectrum sensing messages; noise in at least one radio
channel; the probability for the presence of at least one primary user;
sensing results from at least one second node; request for more, less or
no sensing information; and number of sensing results required to
determine the absence of a primary user.

30-34. (canceled)

Description:

[0001] This disclosure relates generally to sensing in a communication
system, and more particularly to sensing of resource usage in a radio
system.

[0002] A radio communication system can be seen as a facility that enables
radio communication sessions between two or more entities such as mobile
communication devices and/or other stations. In a radio system at least a
part of communications between at least two stations occurs over a
wireless link. Examples of wireless systems include public land mobile
networks (PLMN), satellite based communication systems and different
wireless local networks, for example wireless local area networks (WLAN).
A wireless communication device, or node, is provided with an appropriate
signal receiving and transmitting arrangement for enabling communications
via appropriate channels with other nodes. A communication device may be
arranged to communicate, for example, data for carrying communications
such as voice, electronic mail (email), text message, multimedia, control
information, other data, for enabling internet access and so on.

[0003] Cognitive radio systems have been proposed. A cognitive system
exploits the possibility of secondary users to transmit when no primary
users are present in a given frequency band or do not use another radio
resource at a given time. Primary users can comprise any radio devices,
for example, TV stations, wireless microphones or nodes of cellular
systems. Secondary users can correspondingly be any users who have a
lower priority and/or who can use a resource only when this can be done
without disturbing primary users.

[0004] Cognitive radio typically refers to a device which can detect which
communication channels are in use by primary users and which are not. A
function of a cognitive system is sensing of resource usage, typically
spectrum sensing. This can be generally understood as determination if a
channel or other resource can be used or not by a device. In particular
contexts this can be understood as referring to detection of unused radio
spectrum, or detection of unused radio spectrum by primary users. In the
latter case cognitive devices attempt to sense "spectrum holes". A
spectrum hole is typically a frequency range, where the absence of
primary users has been determined. By detecting particular spectrum hole
or holes and exploiting it or them rapidly, cognitive devices can improve
spectrum utilization.

[0005] Detecting the presence and/or absence of primary users can be a
tedious task. Sensing the presence of primary users with an acceptable
quality can be difficult for a single node. A single detection apparatus
may make errors when determining whether the spectrum is free or not. The
situation can be improved if nodes are allowed to cooperate by exchanging
sensing results. This, however, requires communication between nodes,
usually over a radio link. This information can then be used to control
use of channel resources such that vacant channels are used while
avoiding occupied channels. One technique attempting to provide this is
so-called distributed or co-operative spectrum sensing where sensing
results from more than one secondary device are combined. The combination
of sensing results can enable better detection probability. In an ideal
case, a cognitive radio device receives detection results from all nearby
cognitive radios. In practice, however, this may be impractical due to
the amount of signalling that may become generated.

[0006] The herein described embodiments aim to address one or several of
the above issues.

[0007] In accordance with an embodiment there is provided a method
comprising determining usefulness of resource usage sensing information
in a radio system, and controlling transmission of sensing result
information in the radio system based at least in part on the determined
usefulness.

[0008] In accordance with an embodiment there is provided an apparatus for
a radio system, the apparatus comprising at least one processor, and at
least one memory including computer program code, wherein the at least
one memory and the computer program code are configured, with the at
least one processor, to cause determining of usefulness of a resource
usage sensing result in the radio system and for controlling transmission
of sensing result information at least in part on the determined
usefulness.

[0009] In accordance with an embodiment there is provided an apparatus for
a radio system, the apparatus comprising at least one processor, and at
least one memory including computer program code, wherein the at least
one memory and the computer program code are configured, with the at
least one processor, to cause determining of usefulness of sensing result
information provided in the radio system and sending of a message based
on the determined usefulness of the sensing result information.

[0010] In accordance with an embodiment the determining comprises
determining by a first node the usefulness of the resource usage sensing
information for at least one second node.

[0011] In accordance with a more specific embodiment a first control
apparatus is provided for a first node in a radio system, the first
control apparatus being configured to provide sensing result information
by means of sensing radio resource usage in the radio system and
determining the usefulness of the sensing result for at least one second
node.

[0012] In accordance with an embodiment at least one spectrum sensing is
provided by the first node. The first control apparatus can be configured
to determine usefulness of the result of at least one spectrum sensing.

[0013] In accordance with a more specific embodiment a second control
apparatus is provided for a second node in a radio system, the second
control apparatus being configured to determine usefulness of sensing
result information provided by a first node and to cause sending of the
message to the first node.

[0014] In accordance with an embodiment at least one sensing message is
transmitted. Robustness of the transmission can be adjusted based on the
determined usefulness.

[0015] In accordance with an embodiment a usefulness value of a spectrum
sensing message is estimated for at least one node, at least one
transmission parameter is chosen based on the estimated usefulness value,
and transmission of the spectrum sensing message is controlled using the
chosen at least one transmission parameter.

[0016] In accordance with an embodiment the control comprises controlling
at least one of transmit power, modulation scheme, coding scheme,
quantization scheme, amount of spectrum sensing data, number of
retransmissions, time interval between transmissions of spectrum sensing
messages, use of antennae, and the number of channels reported by the
sensing messaging based on the determined usefulness.

[0017] A parameter based on the usefulness can be determined, and sensing
result messaging can be controlled based on the parameter.

[0018] The control of transmissions may comprise controlling at least one
of unicasting, multicasting and broadcasting a message. The control of
transmissions may also comprise abstaining from sending a spectrum
sensing message.

[0019] The determining of the usefulness can comprise at least one of
estimating number of nodes in the radio system, predicting usability of
sensing information in a future point of time, predicting frequency of
future sensing information messages, estimating level of noise in at
least one radio channel, estimating the probability for the presence of
at least one primary user, considering sensing results from at least one
other node and considering the number of sensing results required to
determine the absence of a primary user.

[0020] The usefulness can be determined by a secondary user, and the
resource usage sensing can comprise detection of usage of resources by
primary users.

[0021] The determining may comprise determining by a second node the
usefulness of resource usage sensing information provided in the radio
system and the controlling may comprise sending from the second node a
message to a first node. Communication may comprise feedback indicative
of usefulness of sensing result information for at least one second node.
Determining of the usefulness can take into account feedback by at least
one second node. The feedback may comprise information about at least one
of usefulness value for sensing information for the reporting at least
one second node, reception quality of a spectrum sensing message, number
of nodes in the radio system, frequency of spectrum sensing messages,
noise in at least one radio channel, the probability for the presence of
at least one primary user, sensing results from at least one second node,
request for more, less or no sensing information and number of sensing
results required to determine the absence of a primary user.

[0022] An unsolicited request regarding sensing information may be
communicated to a node providing sensing information. The request may
relate to at least one of need for sensing information, amount of sensing
information and robustness of the transmission of sensing information.

[0023] A computer program comprising program code means adapted to perform
the herein described methods may also be provided. In accordance with
further embodiments apparatus and/or computer program product that can be
embodied on a computer readable medium for providing at least one of the
above methods is provided.

[0024] Various other aspects and further embodiments are described in the
following detailed description and in the attached claims.

[0025] For a better understanding of some embodiments of the invention,
reference will be made by way of example only to the accompanying
drawings in which:

[0026] FIG. 1 shows a radio system;

[0027]FIG. 2 shows an example of a control apparatus for a communication
device;

[0032] In the following certain exemplifying embodiments are explained
with reference to radio systems and devices. Before explaining in detail
the certain exemplifying embodiments of cognitive radio systems, certain
general principles of wireless communication systems and nodes thereof
are briefly explained with reference to FIGS. 1 and 2 to assist in
understanding of the herein described exemplifying embodiments.

[0033] FIG. 1 shows a plurality of radio devices 100 to 104 referred to
herein as nodes. Nodes 100 to 103 are shown to be in communications with
each other and thus form a radio system. More particularly, a system of
cognitive nodes can be provided by nodes 100 to 103. In general, the
various embodiments of the apparatus and the cognitive radio nodes of
FIG. 1 can include, but are not limited to, mobile devices or terminals
such as cellular telephones or what are known as `smart phones`, personal
digital assistants (PDAs) having wireless communication capabilities,
portable computers (e.g., laptops) having wireless communication
capabilities, image capture devices such as digital cameras having
wireless communication capabilities, gaming devices having wireless
communication capabilities, music storage and playback appliances having
wireless communication capabilities, as well as portable units or
terminals that incorporate combinations of such functions and sensor
networks, wireless access nodes (for example home or office access boxes)
and so on. In other words, a node of a radio system can be provided by
any appropriate radio device or station that is capable of sending and/or
receiving radio signals. Each node may have one or more radio channels
open at the same time and may receive signals from more than one source.
Nodes 100 to 104 may be arranged to use licensed and/or unlicensed bands.

[0034] Nodes 100 to 103 of FIG. 1 are cognitive radio (CR) devices capable
of sensing usage of resources in the radio system. For example, the
cognitive nodes can perform cooperative spectrum sensing and transmit
and/or receive spectrum sensing messages. Spectrum sensing can be
provided by various techniques. For example, spectrum sensing may be
performed by identifying predefined characteristics in a received signal.
Such characteristics may comprise, for example, one or more of a frame
rate, a symbol rate, a symbol duration, a cyclic prefix duration, a known
preamble, a known synchronization sequence, a known reference signal, and
so forth.

[0035] One or more of the radio devices 100 to 104, or any further device,
may act as a primary user having a priority for a given radio resource.
In accordance with an example relating cellular mobile systems a primary
user can be provided with a mobile communication device or station that
can be used for accessing various services and/or applications via a
cellular system. The access can be provided via an access interface
between the mobile user device and an appropriate access node of the
cellular system. An access node can be provided by a base station of a
communication network. Such an access would typically, but not
necessarily, be provided via a licensed band. At the same time some other
nodes in the radio system can be lower priority devices or secondary
users utilising free spectrum if and when it is available. The
arrangement is typically such that the primary user has the right to use
the resource and should not be unnecessarily disturbed by secondary
users.

[0036] In accordance with an example a primary system is provided by a TV
system providing at least one TV channel. In this example the primary
user can be provided by a node broadcasting data on the TV channel or
channels. Secondary users can seek to utilise any TV white space for
their communications.

[0037] Spectrum sensing may attempt to identify transmissions by primary
users, for example based on known signal characteristics. For example, a
cognitive radio sharing a band with one or more primary users such as TV
stations transmitting a signal in accordance with the Digital Video
Broadcasting - Terrestrial (DVB-T) standard may look for signal features
that are unique to the DVB-T. The cognitive radio node may use
statistical analysis on a received signal to identify the replication of
part of a transmitted symbol in a cyclic prefix at a time offset
corresponding to a symbol length supported by the DVB-T standard.

[0038] A cognitive radio device is able to detect primary users and is
configured to avoid causing interference to the primary users. At least
some of the cognitive nodes can collaborate in spectrum sensing, by
sending spectrum sensing information to other nearby cognitive nodes.
Thus, when any of nodes 100 to 103 has performed spectrum sensing, it can
provide the detection result to other nodes in the system by means of
spectrum sensing messaging. This can be done for example via broadcast
signalling, or via multicast or unicast signalling. A receiving node may
then use the results in its determination if it can use the spectrum or
not. The receiving node can, for example, combine its own detection
result and the received detection results. This combined detection result
can then be used to estimate whether the spectrum is primary user free.

[0039] A radio node is provided with appropriate transceiver apparatus. A
node is also typically controlled by at least one appropriate controller
apparatus. FIG. 2 shows an example for a controller apparatus 30 for a
node. The controller apparatus is typically provided with memory capacity
and at least one data processor. FIG. 2 thus shows at least one memory
31, at least one data processing unit 32 and an input/output interface 34
provided by an appropriate radio apparatus. The control apparatus of a
node in accordance with an embodiment can comprise a spectrum sensing
block 33. The control apparatus can be configured to execute appropriate
software applications to provide the desired control functions. The
control apparatus, when provided in a node and comprising at least one
memory and computer program code can be configured, with the at least one
processor, to cause determining how useful a resource usage sensing
provided by the node is in a radio system and subsequently to control
sensing messaging by the node based at least in part on the determined
usefulness. The determination can be made in view of usefulness to one
other node in the radio system or in view of a plurality or even all
nodes in the radio system. More detailed examples for such operation will
be explained in more detail below. At least some of the processing of the
processing blocks may be carried out by one or more processors in
conjunction with one or more memories. The processing block may be
provided by an integrated circuit or a chip set. The control entity can
be interconnected with other control entities.

[0040] The following describes in more details examples of how to minimize
the amount of messages to save power and radio resources whilst
communicating enough sensing information to enable detection of primary
users with a desired probability.

[0041] In ideal case, a cognitive radio node receives detection results
from all nearby cognitive radios. In practice, this may be impractical
due to the amount of signalling this could cause. As spectrum sensing
messages are transmitted over a radio channel they can be subject to
deterioration from noise, interference, channel fading and so forth. In
accordance with an embodiment the likelihood of transmission errors can
be traded off against the amount of radio resources used for transmitting
a message. On the other hand, a node should transmit and/or receive as
little distributed sensing messages as possible to save radio resources
and power but also receive enough sensing information to enable detection
of primary users with appropriate probability.

[0042] To reduce the amount of signalling and processing, it may be that
not all cognitive radio devices 100 to 103 exchange sensing results with
each other. A method for selectively informing other nodes in a radio
system in accordance with an embodiment is shown in FIG. 3 and is
described below with a reference to the nodes of FIG. 1. In this example
transmission of spectrum sensing messages by node 100 is of particular
interest. Node 100 of FIG. 1 performs sensing at 10 to determine usage of
radio resources in the system. For example, node 100 can perform radio
spectrum sensing to detect any use by primary users of the frequency
spectrum. In the example a primary user can be provided by one of nodes
104. At this stage node 100 may detect that there is one or more primary
users occupying some or all of the available radio resources or that the
system is free of primary users. Node 100 may identify a transmission
from a primary user by detecting a known signal characteristic of a
primary user in the received signal, and distinguish it from a signal
transmitted by a secondary user that does not comprise the known signal
characteristic. For example, if a cognitive radio node operates in a band
shared with TV broadcast transmitters as primary users, node 100 may
detect patterns in the received signal that are specific to TV broadcast
transmissions, and based on this conclude that the user is a primary
user.

[0043] After node 100 has performed sensing of used radio resources, it
can process the sensing results, and can initiate the operation to
broadcast the result to its neighbour nodes. Prior to transmission,
however, node 100 can estimate at 12 how valuable its sensing result is
to one or more arbitrary neighbours, or even all neighbours, for example
to nodes 101 and/or 103. As a result of this estimation node 100 can then
determine usefulness of the sensing message in the radio system.

[0044] In determining the usefulness value, node 100 may attempt to
predict a future usefulness of a spectrum sensing message or messages
that is or are to be sent at some point after the sensing. The predicted
usefulness value may depend on the time interval between spectrum sensing
and the transmission of the message. The predicted usefulness value may
further depend on a statistical analysis of the sensing result. For
example, node 100 may intend to transmit the next spectrum sensing
message in 1000 ms (milliseconds). Further, statistical analysis of the
spectrum sensing result may reveal to node 100 that a primary user (for
example a wireless microphone) tends to become active in average every
500 ms. Thus, node 100 may decide that the usefulness value of the result
is to be low because by the time the result is transmitted it is very
likely that resource use by the primary user has already changed.

[0045] In a radio system environment, the usefulness of a single received
sensing message may vary with the environment. For example, if there are
only a few cognitive nodes per area the messages can be more valuable,
because each node has in average only a small number of neighbours. On
the other hand, high density of cognitive nodes can make the sensing
messages less valuable because of high number of neighbours. Node 100 can
utilise an estimate of the density of cognitive nodes and base the
determination of the usefulness for example on the density of nodes in
its neighbourhood. To provide a density estimate node 100 can determine
the number of its neighbouring nodes and estimate the density of nodes
based on the number and the radio coverage area thereof.

[0046] Node 100 can alternatively or in addition determine the frequency
at which it receives sensing messages from other nodes in its vicinity.
High level of transmit activity by secondary nodes can make the sensing
messages more valuable because the increased noise level from secondary
users can make it more difficult to detect a primary user with the
required sensitivity and reliability. Low level of transmit activity by
secondary nodes can make the messages in certain circumstances less
valuable for the recipients because it is easier for the individual nodes
to detect the presence of a primary user themselves.

[0047] However, in some other circumstances different considerations may
be used. For example, the processor apparatus of node 100 can be set to
determine that as long as there is an abundance of sensing messages the
value of a single sensing message can be considered as being relatively
low in the absence of any other indications. If node 100 decides that
sensing messages are scarce and more messages would be required to react
quickly enough, their value can be considered high.

[0048] If node 100 determines that the network is dense and/or sensing
messages are received frequently, node 100 can conclude that the sensing
result is not very valuable to its neighbours. Node 100 can therefore
decide to use less radio resources for the signalling of the sensing
result information. For example, node 100 can decide to use less frequent
transmissions, less transmit power, shorter message with less robust
modulation and/or coding scheme and so on for sending information about
the sensing results. It is even possible that node 100 decides that it
shall not send the results at all.

[0049] On the other hand, if node 100 determines for example that only a
few cooperating nodes are around and/or sensing messages are detected
only sparsely, node 100 can conclude that its result has a high value to
its neighbours. Consequently, node 100 can decide to use more resources,
for example to transmit sensing messages more frequently, with more
power, and/or with more robust modulation and/or coding scheme and so on.

[0050] The control may alternatively or in addition also comprise use of a
different quantization scheme, a different number of retransmissions, use
of different antennae arrangement and a different amount of sensing data
(for example covering a different number of channels) depending on the
determined usefulness value.

[0051] Use of different antenna arrangements can comprise use of different
antenna parameters. For example, the number of transmit antennae in
multiple input multiple output (MIMO) arrangements can be varied. In
accordance with a possibility the type of transmission scheme such as
Alamouti diversity coding or spatial MIMO multiplexing are controlled
based on the usefulness of the sensing results.

[0052] The usefulness can also be determined taking into account other
factors, either alone or in any appropriate combination. For example, a
level of noise in a radio channel can be estimated. The node can then
estimate based on the determined signal-to-noise ratio the reliability of
the sensing result, and use this estimate as a basis of the determination
of the usefulness. The probability for the presence of a primary user can
be estimated. Sensing results from at least one other node can be taken
into account. Frequency of future spectrum sensing messages may be
predicted. The usefulness value of a sensing message can also be
estimated based on the number of sensing results that is required to
determine the absence of a primary user with a given reliability. The
more results are needed the more valuable each message becomes.

[0053] The likelihood of a primary user being present can also be
considered. For example, if a node such as a TV station has been
continuously sensed on a channel for a long time, for example the past
thirty six hours, there is little use to perform aggressive sensing to
catch a short, for example 5 ms "spectrum hole". On the other hand, for a
channel with a history of irregular and bursty transmissions, fast
sensing and messaging may be a good choice.

[0054] Node 100 can then control at 14 transmission of the sensing result
in message M accordingly. Transmission at 14 may comprise a broadcast of
the message M to all neighbours. According to a possibility transmission
at 14 may comprise multicasting the message M to a set of neighbours.
According to another possibility transmission at 14 may comprise
unicasting the message to a single recipient. The identity of recipients
of the message M may be known to node 100, or the recipients may be
anonymous. Recipients may be addressed in unicast transmissions by an
individual node identity or in multicast by a group identity, for
example. The message M can then be received at 16 by neighbours, for
example node 101, who can then use the sensing information included in
the sensing message as it would have been received from any node.

[0055] In accordance with a further embodiment illustrated in FIGS. 4 and
5, a receiving node, for example node 101 in FIGS. 1 and 4, can determine
the usefulness of sensing result information that can be provided in the
system by at least one other node. The node can then send a message to
relevant node or nodes, for example feedback in view of received
information and/or a report in view of its needs. This information can be
delivered as a point-to-point message, by means of broadcasting or by
means of multicasting. The information by node 101 can then be used in
determination of the usefulness by node 100.

[0056] For example, node 101 may determine at 20 how useful the sensing
information it received from node 100 was. It can then report feedback at
22 to node 100 its local situation in this regard. Node 101 can thus take
part in the control of sensing information messaging by reporting how
valuable the spectrum sensing results by node 100 are currently to node
101. Node 100 can receive at 24 feedback information from more than one
node. Node 100 can take the feedback into account at 26 when determining
a usefulness value. In FIG. 3 this would mean taking the feedback into
account at 12 when determining the usefulness.

[0057] In accordance with an embodiment reporting by the receiving node
is, instead of direct feedback, sent spontaneously and not in response to
anything. For example, node 101 may determine that more or less sensing
result information could be useful, and may thus send a message
requesting for more or less sensing information, respectively. The
receiving node may even determine that sensing information from other
nodes is not useful, and accordingly inform the other nodes that it does
not need any further sensing information. Node 101 may also send other
types of request, for example request for more or less robust
transmission, encoding and so on. In accordance with a specific example
the report can be a "one-bit request", for example `0` being indicative
of the need to receive more information / more robust transmission and
`1` less information / less robust transmission. In accordance with
another example the receiving node sends a message informing the sensing
node(s) about its need for sensing information in a scale, for example "9
on the scale of 10".

[0058] The feedback can comprise various types of information. For
example, the feedback can comprise information of the reception quality
of a spectrum sensing message. Number of nodes in the radio system as
detected by the reporting node may also be indicated. An indication of
frequency of received spectrum sensing messages may be provided. The
feedback may also provide information regarding noise in at least one
radio channel. Estimation of the probability for the presence of at least
one primary user by the reporting node may be provided. The reporting
node may also send its own sensing results. The reporting node may also
indicate the number of sensing results it requires to be able to
appropriately determine the presence or absence of a primary user.

[0059] The usefulness value may be quantized to a predetermined range. For
example, the usefulness value may be selected from a range `0` to `10`.
For example, in view of the feedback messaging, value `0` can be used to
indicate that too many spectrum sensing messages are received, and value
`10` at the other end of the scale that the reporting node will not be
able to operate at all without more spectrum sensing results. The
usefulness value may even be quantized to one bit. Value `1` can be used
to indicate, for example, that more spectrum sensing information is
required, and value `0` can be used to indicate that the transmission of
less spectrum sensing information is needed. Use of additional radio
resources for the data transmission can then be controlled accordingly.
In accordance with a possibility the usefulness value may be quantized to
"no bits", and transmission of a message itself from a receiving node may
indicate a need for additional spectrum sensing information.

[0060] In accordance with a further embodiment shown in FIG. 6, node 100
may be in a crowded radio environment with many neighbours while node
101a can be shadowed, for example by walls. This illustrates a situation
where a node can receive messages from fewer neighbours than the other
nodes in the system. In the particular situation of FIG. 6 node 101a can
only receive sensing information from node 100. For this reason node 101a
would benefit from above average number of transmissions of sensing
messages. To provide this, it is possible for node 101a, in response to
detection that it is not receiving enough sensing information, or
information from more than one node, to send a request for more sensing
information to compensate for the lack of sufficient number of sensing
messages.

[0061] Node 100 can determine based on the feedback from node 101a that
the value of its sensing information must be high for node 101a. It can
therefore control its sensing message transmissions such that node 101a
receives sufficient information for the control thereof. The sensing
information can be broadcast so that all nodes receive the message
according to the needs of node 101a, or then node 100 can send one or
more point-to-point sensing messages only to node 101a. For example, node
100 may provide sensing information on specific resources used by node
101a in a point-to-point transmission. Node 100 may optimize the
transmission for reception at node 101a by using pre-coding that uses
known information on the radio channel between node 100 and node 101.
Node 100 may further continue to provide sensing information on a larger
set of resources to all neighbours using another broadcast message.

[0062] It is noted that although the term radio system is used herein
cooperative sensing does not require any established network
infrastructure. For example, the relevant nodes may simply broadcast
information about their sensing results periodically. Therefore, node 100
is not necessarily concerned about the actual identities of the
cooperating nodes such as nodes 101 or 103. The term radio system can
thus be understood as referring to radio devices that can use same
resources.

[0063] Co-operative sensing can be provided via cognitive control
signalling. This can be provided as a part of a cognitive control network
functionality. Signalling between cognitive nodes of a cognitive control
network may be performed via physical radio links, either permanently or
temporarily as specified for this purpose. According to a possibility the
signalling can be provided via logical links, for example such that
cognitive control signalling between cognitive nodes is arranged via a
server, such as an Internet Protocol (IP) server.

[0064] It is noted that the radio technology for control signalling
between cognitive nodes can be different than the radio technology for
data transmission between the same nodes.

[0065] In accordance with an embodiment a node provides the sensing
facility of a radio system and informs the other nodes accordingly,
taking the usefulness of its sensing results into account. According to
an alternative a few cognitive nodes, but not all cognitive nodes, of a
radio system are provided with a sensing capability.

[0066] It should be appreciated that the embodiments may be applied in any
current or future standard or non-standard radio system that supports
cognitive radios and/or comprises a plurality of cognitive radios. The
access may be based on code division multiple access (CDMA), or wideband
CDMA (WCDMA), orthogonal frequency-division multiple access (OFDMA), time
division multiple access (TDMA), frequency division multiple access
(FDMA), space division multiple access (SDMA) and so on. As non-limiting
examples, aspects of the exemplary embodiments of the invention may be
implemented in a wireless local area network (WLAN) and/or WiMax
(Worldwide Interoperability for Microwave Access), in cellular access
networks such as third Generation Partnership Project (3GPP) universal
terrestrial radio access network (UMTS) terrestrial radio access network
(UTRAN) or evolved UTRAN (E-UTRAN) based wireless communication system.
Nodes 100 to 110 may be arranged to support one or more cognitive
technologies to communicate detection estimates with each other. For
instance, a device may be arranged to support at least one of IEEE 802.15
specification describing a system using unlicensed bands, the IEEE 802.22
working group developing a standard for a system operating on unused
television channels and third Generation Partnership Project (3GPP) long
term evolution (LTE) cognitive radio features. It shall be appreciated
that these are non-limiting examples only, and that the herein described
principles may be applied in any system where detection of used radio
resources and control of transmission of the results is desired.
Therefore, although certain embodiments were described above by way of
example with reference to certain exemplifying architectures for wireless
networks, technologies and standards, embodiments may be applied to any
other suitable forms of communication systems than those illustrated and
described herein.

[0067] The required data processing apparatus and functions of a node of
the radio system may be provided by means of one or more data processors.
The described functions may be provided by separate processors or by an
integrated processor. The data processors may be of any type suitable to
the local technical environment, and may include one or more of general
purpose computers, special purpose computers, microprocessors, digital
signal processors (DSPs), application specific integrated circuits
(ASIC), a field programmable gate array (FPGA), gate level circuits and
processors based on multi-core processor architecture, as non-limiting
examples. The data processing may be distributed across several data
processing modules. A data processor may be provided by means of, for
example, at least one chip. Appropriate memory capacity can also be
provided in the relevant devices. The memory or memories may be of any
type suitable to the local technical environment and may be implemented
using any suitable data storage technology, such as semiconductor-based
memory devices, magnetic memory devices and systems, optical memory
devices and systems, fixed memory and removable memory.

[0068] An appropriately adapted computer program code product or products
may be used for implementing the embodiments, when loaded or otherwise
provided on an appropriate data processing apparatus, for example for
controlling sensing operations, for estimating usefulness of the sensing
results, for determining an appropriate usefulness value based thereon,
and for controlling communications of sensing information from a node to
one or more receiving nodes. Similarly, a program code product can be
used at a node receiving the sensing reports, for example for generating
feedback reports and causing transmission thereof. The program code
product for providing the operation may be stored on, provided and
embodied by means of an appropriate carrier medium. An appropriate
computer program can be embodied on a computer readable record medium. A
possibility is to download the program code product via a data network.
In general, the various embodiments may be implemented in hardware or
special purpose circuits, software, logic or any combination thereof.
Embodiments of the inventions may thus be practiced in various components
such as integrated circuit modules. The design of integrated circuits is
by and large a highly automated process. Complex and powerful software
tools are available for converting a logic level design into a
semiconductor circuit design ready to be etched and formed on a
semiconductor substrate.

[0069] The herein described exemplifying embodiments can provide a
variable trade-off between reliability and resource use for the
signalling of spectrum sensing information. Some of the embodiment can be
provide adapting of a cooperative sensing scheme to the prevailing radio
environment such that it takes both cognitive secondary and primary users
into account. Power consumption of battery-powered devices may also be
taken intro consideration.

[0070] It is also noted herein that while the above describes exemplifying
embodiments of the invention, there are several variations and
modifications which may be made to the disclosed solution without
departing from the spirit and scope of the present invention.

[0071] In accordance with certain aspects the invention may be embodied as
follows.

[0072] As a method comprising:

[0073] determining by a node usefulness
of resource usage sensing information in a radio system; and

[0074]
controlling transmission of sensing information by the node based at
least in part on the determined usefulness.

[0075] The method according to above, where the determining comprises
determining by the node the usefulness of the resource usage sensing
information for at least one second node.

[0076] The method according to above, comprising:

[0077] performing at
least one spectrum sensing by the first node, and

[0078] determining
usefulness of the result of the at least one spectrum sensing for at
least one second node.

[0079] The method according to above, comprising transmitting at least one
sensing message, wherein the controlling comprises adjustment of
robustness of the transmission based on the determined usefulness.

[0080] The method according to above, comprising:

[0081] estimating a
usefulness value of a spectrum sensing message for at least one node;

[0082] choosing at least one transmission parameter based on the
estimated usefulness value; and

[0083] controlling transmission of the
spectrum sensing message using the chosen at least one transmission
parameter.

[0084] The method according to above, comprising controlling at least one
of transmit power, modulation scheme, coding scheme, quantization scheme,
amount of spectrum sensing data, number of retransmissions, time interval
between transmissions of spectrum sensing messages, use of antennae, and
the number of channels reported by the sensing messaging based on the
determined usefulness.

[0085] The method according to above, where the determining of the
usefulness comprises at least one of:

[0086] estimating number of nodes
in the radio system;

[0087] predicting usability of sensing information
in a future point of time;

[0088] predicting frequency of future sensing
information messages;

[0089] estimating level of noise in at least one
radio channel;

[0090] estimating the probability for the presence of at
least one primary user;

[0091] considering sensing results from at least
one other node;

[0092] considering the number of sensing results required
to determine the absence of a primary user; and

[0093] taking into
account feedback by at least one second node.

[0094] As a method comprising:

[0095] determining usefulness of resource
usage sensing information for a node in a radio system, and

[0096]
sending from the node a message based on the determined usefulness of the
resource usage sensing information.

[0097] The method according to above, comprising sending a message
containing information about at least one of:

[0098] feedback
indicative of usefulness of sensing result information received from at
least one second node;

[0099] reception quality of a spectrum sensing
message;

[0100] number of nodes in the radio system;

[0101] frequency of
spectrum sensing messages;

[0102] noise in at least one radio channel;

[0103] the probability for the presence of at least one primary user;

[0104] sensing results by the node;

[0105] a request for more, less or no
sensing information; and

[0106] number of sensing results required to
determine the absence of a primary user.

[0107] As an apparatus for a radio system, the apparatus comprising:

[0108] at least one processor, and

[0109] at least one memory including
computer program code,

[0110] wherein the at least one memory and the
computer program code are configured, with the at least one processor, to
cause determining of usefulness of a resource usage sensing result in the
radio system and for controlling transmission of sensing result
information at least in part on the determined usefulness.

[0111] The apparatus according to above, comprising a control apparatus
for a node in the radio system, the control apparatus being configured to
cause sensing of radio resource usage in the radio system, to provide
sensing result information based on the sensed radio resource usage, and
to determine the usefulness of the sensing result information for at
least one second node.

[0112] The apparatus according to above, where the apparatus is configured
to determine usefulness of the result of at least one spectrum sensing.

[0113] The apparatus according to above, wherein the apparatus is
configured to control transmission of sensing result messages based on
adjustment of robustness of the transmission based on the determined
usefulness.

[0114] The apparatus according to above, wherein the apparatus is
configured to control at least one of transmit power, modulation scheme,
coding scheme, quantization scheme, amount of spectrum sensing data,
number of retransmissions, time interval between transmissions of
spectrum sensing messages, use of antennae, and the number of channels
reported in sensing result information messages.

[0115] The apparatus according to above, wherein the apparatus is
configured to at least one of:

[0116] estimate number of nodes in the
radio system;

[0117] predict usability of sensing information in a future
point of time;

[0118] predict frequency of future sensing information
messages;

[0119] estimate level of noise in at least one radio channel;

[0120] estimate the probability for the presence of at least one primary
user;

[0121] consider sensing results from at least one other node;

[0122] consider the number of sensing results required to determine the
absence of a primary user; and

[0123] take into account feedback
information from at least one other node.

[0124] The apparatus according to above, wherein the apparatus is
configured to sense usage of resources by primary users and to report
results of the sensing to at least one secondary user.

[0125] As an apparatus for a radio system, the apparatus comprising:

[0126] at least one processor, and

[0127] at least one memory including
computer program code, wherein the at least one memory and the computer
program code are configured, with the at least one processor, to cause
determining of usefulness of sensing result information provided in the
radio system and sending of a message based on the determined usefulness
of the sensing result information.

[0128] The apparatus according to above, comprising a control apparatus
for a node in the radio system, the control apparatus being configured to
determine usefulness of sensing result information provided by another
node and to send the message to the other node.

[0129] The apparatus according to above, wherein the apparatus is
configured to send feedback indicative of usefulness of sensing result
information received from at least one other node.

[0130] The apparatus according to above, where the message contains
information about at least one of:

[0131] usefulness of sensing
information received from at least one other node;

[0132] reception
quality of a spectrum sensing message;

[0133] number of nodes in the
radio system;

[0134] frequency of spectrum sensing messages;

[0135] noise
in at least one radio channel;

[0136] the probability for the presence of
at least one primary user;

[0137] sensing results by the node;

[0138]
request for more, less or no sensing information; and

[0139] number of
sensing results required to determine the absence of a primary user.

Patent applications by Markus Nentwig, Helsinki FI

Patent applications by Niko Tapani Kiukkonen, Veikkola FI

Patent applications by NOKIA CORPORATION

Patent applications in class Having measuring, testing, or monitoring of system or part

Patent applications in all subclasses Having measuring, testing, or monitoring of system or part